The invention relates to a capped electric lamp of the type having a translucent lamp vessel sealed in a vacuum-tight manner, filled with gas and having a longitudinal axis in which an electric element is arranged, current supply conductors extending from the electric element through the lamp vessel to the exterior. A metal clamping member surrounds with clamping fit a longitudinal part of the lamp vessel. The lamp has a lamp cap of insulating material provided with a cup-shaped part with a continuous wall portion and a base portion and having contact members projecting beyond the cup-shaped part. A substantially circular-cylindrical metal sleeve is fixed in the cup-shaped part of the lamp cap and has an end projecting beyond said part by. The metal clamping member connected to the metal sleeve and the current supply conductors are connected to a respective contact member of the lamp cap.
Such a capped electric lamp is known from EP O 193 997-A1 which corresponds to U.S. Pat. No. 4,687,965. The known lamp is intended to be used as a vehicle headlight lamp.
The said Application discloses an electric lamp, in which the electric element is a transversely arranged filament. The lamp vessel is therefore fairly broad and the seal of the lamp vessel is fairly wide. Through this seal, two or more current supply conductors are passed to the exterior. The known incandescent lamp is therefore very suitable to be used with a metal clamping member consisting of a plate provided with an opening, in which the lamp vessel is held by vanes formed at said plate along said opening. The plate has a cylindrical flanged edge, which is welded to the metal sleeve.
In an electric lamp having a comparatively narrow lamp vessel, such as, for example, the electric discharge lamp according to GB No. 2 132 011 B which corresponds to U.S. Pat. No. 4,594,529, the lamp vessel does not provide for sufficient grip for the known plate-shaped clamping member to be secured to the lamp cap by means thereof.
For electric lamps used in an optical system, such as vehicle headlights, however, it is of great importance that the electric element occupies an accurately defined position with respect to the lamp cap so that with a defined positioning of the lamp cap with respect to a headlight reflector the electric element occupies the correct position in this reflector. This is necessary to obtain a good light beam from such a headlight, which is not dazzling.
EP 0224 954 A1 which corresponds to U.S. application Ser. No. 932,955 filed Nov. 19, 1986, discloses a capped vehicle headlight lamp, in which the comparatively narrow lamp vessel is secured by its current supply conductors electrically, but also mechanically, to conductors arranged in the lamp cap. In case the current supply conductors are comparatively thin and hence are mechanically weak, it is objectionable to secure the lamp vessel also mechanically to the lamp cap only by means of said current-supply conductors.
In this known vehicle headlight lamp, it is further not always possible to secure the lamp vessel in a sufficiently aligned state to the lamp cap, for example if the electric element is not wholly concentrically arranged in the lamp vessel.